Insulator



Oct. 1, 1929. Y H. B. SMITH INSULATOR Filed July 13,

E WM m a ATTORNEY WITNESSES:

Patented Oct. 1, 1929 UNITED STATES PATENT! OFFICE HAROLD B. SMITH, OF. WORCESTER, MASSACHUSETTS, ASSIGNORTO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA IN SULATOB Application flied July 18,

Myinvention relatesto insulators and par ticularly to insulators for supporting the conductors of high-potential circuits.

One object of my invention is to provide a high-voltage insulator that shall so direct, widely distribute and confine the electrostatic field thereof as to greatly increase the breakdown value of the insulator, to prevent arcing to surrounding objects and to prolong the life of the insulator.

Another object of my invention is to provide an insulator that shall accomplish the above object, and, at the same time, be extremely simple and durable in construction and economical to manufacture.

Another object of my invention is to provide a high-voltage insulator in which the refractory .or vitreous insulating member or members may be reduced to substantially the utmost simplicity in shape, thereby economizing in, and greatly facilitating, the manufacture thereof, and to provide an insulator in which the refractory or vitreous insulating members may be eliminated entirely.

A further object of my invention is to provide an insulator of the rigid pin ty e, in which the pin is so mechanically reinfbrced and disposed relative to its supporting arm or member as to permit the arcing terminal of the insulator to be placed a safe arcing distance from the supportin member and in which the pin is also so adapted for mounting on the supporting member as to permit the latter, when found advisable, to be a wooden cross arm which will not be; materially weakened by the mounting of the pin thereon, as in structures in which the pin fits directly in an opening in the arm.

In my copending a plications for Letters Patent on insulators, erial Nos. 548,818, filedv April 1,1922, and 559,743, filed Ma 10, 1922, and assigned to the Westinghouse hlectric & Manufacturing Compan are set forth principlesfor improving t e construction and operation of high-voltage insulators which are embodied in my present invention and so combined with other features as to render my resent invention an important step in the evelopment of the high-potential insulator art.

1m. Serial Io. 651,245.

In the first of the above-mentioned appli cations, Serial N 0. 548,818, there is set forth the feature of widely distributing and definitely directing the electrostatic stresses away from an insulatorsurface. In the second application, Serial No. 559,743, the feature of providing a water-drip portion outside the zone of maximum potential gradient in the electrostatic field is set forth, both as a distinct feature and in combination with the features of the first said application.

In my present invention, the above-mentioned features are embodied in the form of new and improved structures, in combination with each other and with means for me chanically reinforcing the insulator and preventing arcin to the insulator support.

Figure 1 o the accompanying drawing is a side view, partially in elevation and partially in section, of an insulator constructed in accordance with my invention, and

Fig. 2 is asimilar view of a modified form thereof.

The insulator of my invention comprises, in general, a main insulating body member 1, such as a pin or column, a member 2 for attaching a conductor 3 thereto, an upper terminal member 4 and a lower conducting terminal member 5 for attachment to any suitable support 6, such as a cross-arm of a transmission pole or tower.

As shown in Fig. 1, the insulating column 1 comprises a pin 7, preferably of fibrous material such as impregnated wood, paper, cloth or other suitable material, having a lower portion 8 for mounting in the terminal member 5, a frusto-conical portion 9 and a portion 10 which may be screw-threaded or otherwise constructed for the reception of a refractory or vitreous insulating cap or bushing 11. The latter being of relatively simple cup-shape is comparatively easy to manufacture.

The lower terminal member 5 is constructed to have a socket portion 12 that extends, from a base portion 14. adjacent to the supporting member 6, for a relatively great distance along the lower end of the pin 7 The construction is provided for a twofold pur pose, the first being to mechanically reinforce .ciples set forth cated byv dotted lines, away concentrating,

the pin 7 to increase its bending moment relative to the base portion .14 and the second being to so dispose both the upper terminal member 4 and a flux-distributing toroidal member or portion 15 on the lower terminal member '5 a sufiicient distance from the supporting member 6 as to prevent arcing to the latter, as will hereinafter be more fully pointed out. Y

The member 5, with its base portion 14 somewhat wider than "the remainder thereof to provide a stable and substantial support for the pin, is preferably secured to the supporting member 6 by a bolt 16 of relatively small diameter, which construction, if the member 6 beef the ordinary wood cross-arm variety, retains much of the original strength of the cross-arm by requiring only a small opening for the reception of the bolt 16.

While the portion 15 always takes the are, it is not an arcing member .in the ordinary sense of the word, as compared with former arcing members on high-potential insulators,

As formerly employed, most arcing members for insulators have been in the form of pointed horns or in the form of rings of small diameter in the dimensions corresponding to the dimension X in Fig. 1. This construction serves to concentrate the field and to cause breakdown of the field at a voltage much lower than would be the case if the insulator were constructed in accordance with the prinin my above-mentioned copending application, Serial No. 548,818.

"As set forth in that application relative to a similar member, the member 15 is constructed to have the dimension X relatively great and to have the entire, body of the annular arcing portion of the member in spaced relation to the insulating column 1. This construction draws or attracts the field, as indifrom the insulator l without concentrating the field unduly as with the usual arcing horns or rings. Thus, while the arc ultimately breaks on the member 15 and it is in this sense an arcing member, by widely distributing, instead of the field'at the arcing point, the break-down or arcing voltage for an insulator of the same spacing is greatly increased.

The upper: terminal member is, of course, formed to assist the lower terminal member in thus widely distributing and directing the field and in the copending application Serial No. 548,818 above mentioned, is shown as comprising a relatively thick insulating member of substantially bowl-s ape having a conducting surface.

In my present invention, the upper terminal member 4 is preferably constructed of a single integral member of sheet metal, embodyin'g in one piece, not only the stress distributing and directing features of one of the above mentioned co-pending applications, but

also the feature of removing the rain drip from the field of maximum potential gradient, as set forth in the other co-pending application. In the latter, there are two members, one for distributing and directing the field and the other for removing the rain drip.

The member 4 of my present invention, is adapted for the double purpose, set forth above, by providing it with an annular curved toroidal portion 18, between the insulating column 1 and an outer perimetral drip portion 19, that bows or projects toward the lower member 15 to be closer to the latter than any other portion of the member 4. Thus, a line 20, extending between the portions 18 and 15, represents the shortest distance anywhere between the upper and lower terminal members. i

If the line 20 be carried, counterclockwise as viewed in the drawing, around the center of the member 15, it will be seen that it intercepts a vertical line 21 at a distance below the drip portion 19 which is suflicient to prevent the are taking oil to the bottom of the longest continuous rain stream which is likely to pour over the portion 19 and this distance may be readily increased by increasing the diameter of the drip portion 19 or by shortening the distance represented by the line 20.

By providing the socket portion 12 and the. arcing portion 15, a certain distance above the supporting member 6,-the distance represented by the line 21 may be made such as to effectually prevent the arc travelling to the supporting member 6 under substantially all wet and dry conditions. I

As represented by the dotted lines in Fig. 1, the dielectric field of greatest intensity is along the line 20 between the members 15 and 18, and that, on either side of the line 20, the field gets gradually weaker substantially in proportion to its distance from the line 20. Thus, as the surface of the column 1 is ap-- proached, the field is so weak as to never permit an arc to impinge thereagainst. This feature is morefully pointed out in my copending application, Serial No. 548,818, hereinbefore referred to.

As further shown in Fig. 1, the pin 7 may be protected against the weather by a preferably plain vitreous insulating sleeve 23 which may be formed integral on the cap 11 or be cemented or otherwise secured thereto. The

"upper terminal member 4 may be provided or suitable means may be employed to secure the conductor 3 in position.

The field-distributing portion 1-5 is mounted on the socket portion 12 by an annular portion 29 having apertures 30 therein, or by a series of spaced radial portions constituting substantially the same thing. This construction prevents the accumulation of water within the portion 15 which, if it were to become level full with water, would impair its field directing characteristics and cause a more concentrated field on the insulating column-adjacent to the member 15.

In the device of Fig. 2, in which similar parts are designated by similar reference characters, the construction and operation are substantially the same as in the device of Fig. 1, with the exception that the vitreous members 11 and 23 are omitted and the pin 7 is of uniform construction, extending between the terminal members 4 and 5.

Since it is only the weather and not charring from corona and arcs, which the pin 7 need be protected against, if the pin 7 is properly treated, as by water-proof impregnation, it should be effective during a period equal to many times the life of a similar or ordinary pin used in connection with insulators as formerly constructed.

By my invention, an extremely simple, compact, rugged and economical insulator is provided which improves the operation of high-potential transmission lines, requires a minimum of attention and has a much greater life than insulators heretofore used in similar service.

WVhile I have shown and described particular forms of my invention, changes may be effected therein without departing from the spirit and scope thereof, as set forth in the appended claims.

I claim as my invention:

1. An insulator comprising an elongated insulating member, an upper terminal member having a conductmg substantially toroidal surface portion of relatively great area surrounding the insulating member in widely radially-spaced relation thereto at a position downwardly removed from the upper end thereof, said surface portion merging, at its inner portion, into a conducting surface portion of inverted substantially bowl shape and an annular portion extending laterally from the outer portion of said toroidal surface portion to an annular waterdrip portion disposed laterally-outwardly therebeyond, and a lower terminal member having a conducting substantially toroidal surface portion of relatively great area surrounding the insulating member in-radiallyspaced relation thereto, the space surrounding the insulating member between that member and the lower toroidal surface portion, andfor a relatively great distance below the latter portion, being open to prevent interference with the electrostatic field between said lower toroidal-surface portion and that of the upper terminal member.

2. An insulator comprising an elongated insulating member, an upper terminal structureincluding a single integral member having a conducting substantially toroidal surface portion of relatively great area sur-' rounding the insula ing member in widely to, the space surrounding the insulating mem-- ber between that member and the lower toroidal surface portion, and for a relatively great distance below the latter portion, being-open to prevent interference with the electrostatic field between said lower toroidalsurface portion and that of the upper terminal member.

3. An insulator comprising an elongated insulating member, an upper terminal struc ture including a sheet-metal member having a substantially toroidal portion of relatively great area surrounding the insulating member in widely radially-spaced relation thereto at a position downwardly removed from the upper end thereof, said toroidal portion merging at its inner portion into a portion of inverted substantially bowl shape and an annular portion continuing laterally from the outer portion of said toroidal portion to an annular water-drip portion disposed laterally outwardly therefrom, and a lower terminal member having a conducting substantially toroidal surface portion of relativel great area surounding the insulating mem er in radially-spaced relation thereto, the space surrounding the insulating member between that member and the lower 15 toroidal surface portion, and for a relatively great distance below the latter portion, being open to prevent interference with the electrostatic field between said lower toroidalsurface portion andthat of the upper termi- 12o 

